Process for the production of polyol ethers

ABSTRACT

A process for the production of polyol ethers comprising the steps of 
     A) reacting a mixture of at least one polyol and at least one carbonyl compound of the formula 
     
         R.sup.1 --CO--R.sup.2                                      (I) 
    
      in which R 1  and R 2  independently of one another represent hydrogen or aliphatic hydrocarbon radicals containing 1 to 22 carbon atoms and 0, 1, 2, or 3 double bonds, with hydrogen at an elevated temperature in the presence of a hydrogenation catalyst which is insoluble in the reaction mixture; and 
     B) removing the polyol ether-containing reaction product from the catalyst.

This application is 371 of PCT/EP92/01587 filed Jul. 13, 1992.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a process for the production of polyol ethersby catalytic reaction of mixtures of polyols and carbonyl compounds withhydrogen at elevated temperatures and under elevated pressure.

2. Statement of Related Art

Ethers of polyols, for example glycerol ethers, are surface-activesubstances which have excellent detergent properties and which may beused, for example, as wetting agents (U.S. Pat. No. 2,932,670),emulsifiers (DE 11 00 035 A1)] or lime soap dispersants (U.S. Pat. No.3,350,460).

Polyol ethers are generally produced by WILLIAMSON'S ether synthesis. Inthis process, polyols, for example glycerol, are reacted with alkylhalides in the presence of strong bases. According to DE-PS 615 171,alkali metal salts of alkyl sulfates may be used instead of the alkylhalides.

However, the known processes mentioned above all have the disadvantagethat the production of the polyol ethers is accompanied by theaccumulation of salts, for example potassium chloride or sodium sulfate,which cannot remain in the product, but instead have to be removed--insome cases with considerable effort.

Another serious disadvantage is that these salts are by no means pure,but instead are contaminated with significant quantities of product.Accordingly, the disposal of these waste materials is extremelyexpensive and adversely affects the profitability of the process.

Accordingly, the problem addressed by the present invention was toprovide a process for the production of polyol ethers which would befree from the disadvantages mentioned above.

DESCRIPTION OF THE INVENTION

The present invention relates to a process for the production of polyolethers which is characterized in that mixtures containing

a) polyols and

b) carbonyl compounds corresponding to formula (I):

    R.sup.1 --CO--R.sup.2                                      (I)

in which R¹ and R² independently of one another represent hydrogen oraliphatic hydrocarbon radicals containing 1 to 22 carbon atoms and 0, 1,2 or 3 double bonds,

are reacted with hydrogen at elevated temperatures and under elevatedpressure in the presence of a catalyst which is insoluble in thereaction mixture.

It has surprisingly been found that polyol ethers can be producedwithout the formation of salts as secondary products providing thepolyols are reacted with aldehydes or ketones and the acetals or ketalsintermediately formed are simultaneously subjected, i.e. withoutisolation, to catalytic hydrogenation.

Polyols are compounds which contain at least two hydroxy groups. Typicalexamples are ethylene glycol, diethylene glycol, triethylene glycol,polyethylene glycols having an average molecular weight of 300 to 1500,propylene glycol, polypropylene glycols having an average molecularweight of 300 to 1500, propane-1,2diol, propane-1,3-diol,butane-1,2-diol, butane-1,4-diol, average molecular weight of 300 to1500, propane-1,2diol, propane-1,3-diol, butane-1,2-diol,butane-1,4-diol, glycerol, monoesters of glycerol with C₆₋₂₂ fattyacids, diglycerol, oligoglycerols with an average degree of condensationof 3 to 10, trimethylol propane or pentaerythritol. It is particularlypreferred to use glycerol.

The carbonyl compounds corresponding to formula (I) are known aldehydesand ketones which may be prepared by methods known per se. Carbonylcompounds corresponding to formula (I), in which R¹ and R² independentlyof one another represent C₁₋₁₈ alkyl groups, are preferably used.

Typical aldehydes are, for example, formaldehyde, acetaldehyde,acrolein, propionaldehyde, butyraldehyde, croton aldehyde, caproicaldehyde, caprylic aldehyde, capric aldehyde, lauryl aldehyde, myristylaldehyde, cetyl aldehyde, stearyl aldehyde, oleyl aldehyde, elaidylaldehyde, linolyl aldehyde, linolenyl aldehyde, behenyl aldehyde orerucyl aldehyde.

Typical ketones are, for example, acetone and the various positionisomers of butanone, pentanone, hexanone and octanone and also the fattyketones obtained by pyrolysis of the alkaline earth metal salts ofC₁₂₋₂₂ fatty acids. It is particularly preferred to use acetone.

The polyols and the carbonyl compounds may be used in a molar ratio of5:1 to 1:5 and preferably in a molar ratio of 1:1 to 1:4.

The hydrogenation may be carried out heterogeneously, i.e. in thepresence of a catalyst which is not soluble in the reaction mixture andwhich may therefore be separated from the product with minimal effortafter the reaction and recovered. A typical example of this is the useof transition metals such as, for example, nickel, cobalt, platinum,rhodium, ruthenium or, in particular, palladium. It is advisable to usethe catalysts in finely divided form, for example as platinum sponge orpalladium black or even in the form of gauzes. To carry out the processaccording to the invention on an industrial scale, it has proved to beoptimal to fix fine-particle metal to an inorganic support, for examplesilicon dioxide, aluminium oxide or, in particular, active carbon. It ispreferred to use palladium on active carbon, the Pd content of thecatalyst being from 1 to 15% by weight and preferably from 5 to 15% byweight, based on the catalyst (metal+support). If the reaction iscarried out continuously, it is advisable to use a fixed bed in whichthe catalyst is arranged, for example in the form of pellets.

In the reaction with hydrogen, the catalyst may be used in a quantity of1 to 15% by weight and is preferably used in a quantity of 5 to 10% byweight, based on the starting materials.

The reaction may be carried out discontinuously or continuously. Forexample, the starting materials--polyol and carbonyl compound--may beintroduced into a pressure vessel, for example a steel autoclave, and,after addition of the catalyst, the reaction mixture is exposed tohydrogen. Elevated temperatures and excess pressure are necessary forthe acetalization or ketalization of the polyols and the simultaneoushydrogenation of the acetals or ketals formed as intermediate products.The reaction may be carried out at temperatures of 150° to 250° C. andunder pressures of 50 to 150 bar. To obtain a high yield of monoethersand bisethers, it has proved to be optimal to select a temperature rangeof 175° to 200° C. and a pressure range of 75 to 125 bar.

In one preferred embodiment of the process according to the invention,the reaction may be carried out continuously, for example using afixed-bed reactor. In this case, it has proved to be of particularadvantage to carry out the reaction with a liquid hourly space velocityLHSV (corresponding to the throughput per reactor volume and unit oftime) of 0.05 to 0.7 and preferably 0.1 to 0.3 h⁻¹.

The various position-isomeric polyol monoethers and bisethers may beobtained in yields of 35 to 50% of the theoretical by the processaccording to the invention. The secondary products are, above all,acetals or ketals, acetal ethers or ketal ethers and the hydrogenationproducts of the carbonyl compounds used. If desired, the polyol ethersmay be enriched by removing the secondary products and unreacted polyolby distillation and returning them to the reaction. This affords thepossibility of recycling which is particularly advantageous in regard tohigh yields of polyol ethers.

Industrial Applications

The polyol ethers obtainable by the process according to the inventionhave surface-active and solubilizing properties and are suitable for theproduction of solubilizers, emulsifiers, lime soap dispersants, wettingagents and detergency boosters, in which they may be present inquantities of 1 to 50% by weight and preferably 10 to 25% by weight,based on the particular preparation.

The following Examples are intended to illustrate the invention withoutlimiting it in any way.

EXAMPLES Example 1

Discontinuous hydrogenation.

A mixture of 46 g (0.5 mole) of glycerol and 58 g (1.0 mole) of acetoneis introduced into a 250 ml steel autoclave, followed by theintroduction of 10 g of hydrogenation catalyst (5% by weight ofpalladium on active carbon)--corresponding to around 10% by weight,based on the starting materials. The autoclave was closed and hydrogenwas admitted at a temperature of 175° C. until a pressure of 100 bar hadbeen established. After termination of the reaction, the autoclave wascooled and vented and the catalyst was filtered off from the liquidphase. The reaction product had the following composition:

    ______________________________________                                        1- or 2-glycerol monoisopropyl                                                                       36% by weight                                          ether (ME)                                                                    1,2- or 1,3-glycerol-bis-isopropyl                                                                   10% by weight                                          ether (BE)                                                                    Glycerol isopropyl ketal (K)                                                                         --                                                     Glycerol monoisopropyl ether ketal (EK)                                                              1% by weight                                           Glycerol (G)           13% by weight                                          Isopropyl alcohol (iPA)                                                                              40% by weight                                          ______________________________________                                    

Example 2

65 g (0.7 mole) of glycerol, 40 g (0.91 mole) of acetaldehyde and 10 gof palladium on active carbon (Pd content 5% by weight, based on thecatalyst) were reacted as in Example 1. The reaction was carried outover a period of 6 h at a temperature of 175° C. and under a hydrogenpressure of 100 bar. After the ethanol formed had been distilled off, aproduct having the following

    ______________________________________                                        1- or 2-glycerol monoethyl ether                                                                     39% by weight                                          1,2- or 1,3-glycerol bis-ethyl ether                                                                 8% by weight                                           Glycerol               53% by weight                                          ______________________________________                                        composition was obtained:

Examples 3 to 5

Continuous hydrogenation.

In a fixed-bed hydrogenation reactor (capacity 1000 cm³), a mixture ofacetone and glycerol in a molar ratio of 2.5:1 was continuouslyhydrogenated on a pelleted palladium/active carbon catalyst (5% byweight Pd, based on the catalyst) at a temperature of 200° C. and undera pressure of 100 bar. The LHSV was 0.18 to 0.7 h⁻¹. The compositionofthe reaction products is shown in Table 1. No reduction in activityand no significant change in the composition of the products wereobserved over aperiod of 14 d.

                  TABLE 1                                                         ______________________________________                                        Continuous hydrogenation of acetone/glycerol                                  Percentages in % by weight                                                          LHSV     ME      BE    K    EK    G    iPA                              Ex.   h.sup.-1 %       %     %    %     %    %                                ______________________________________                                        3     0.18     41      6     10   7     31   5                                4     0.30     39      6     7    5     37   6                                5     0.70     29      5     4    3     53   6                                ______________________________________                                    

We claim:
 1. A process for the production of polyol ethers comprisingthe steps ofA) reacting a mixture of at least one polyol and at leastone carbonyl compound of the formula

    R.sup.1 --CO--R.sup.2                                      (I)

in which R¹ and R² independently of one another represent hydrogen oraliphatic hydrocarbon radicals containing 1 to 22 carbon atoms and 0, 1,2 or 3 double bonds, with hydrogen at an elevated temperature in thepresence of a catalyst consisting of a hydrogenation catalyst which isinsoluble in the reaction mixture; and B) separating the polyolether-containing reaction product from the catalyst.
 2. The process ofclaim 1 wherein the molar ratio of polyol to carbonyl compound in stepA) is from 5:1 to 1:5.
 3. The process of claim 2 wherein said ratio isfrom 1:1 to 1:4.
 4. The process of claim 1 wherein in step A) the atleast one polyol is glycerol.
 5. The process of claim 1 wherein in stepA) in the at least one carbonyl compound R¹ and R² independently of oneanother represent C₁₋₁₈ alkyl groups.
 6. The process of claim 5 whereinthe at least one carbonyl compound is acetone.
 7. The process of claim 1wherein in step A the hydrogenation catalyst is present in from 1 to 15%by weight, based on the weight of said mixture.
 8. The process of claim7 wherein from 5 to 10% by weight of hydrogenation catalyst is present.9. The process of claim 7 wherein the hydrogenation catalyst consists ispalladium, optionally present on an inorganic support.
 10. The processof claim 9 wherein from 5 to 15% by weight of palladium is present. 11.The process of claim 1 wherein step A) is carried out at a temperaturein the range of from 150° to 250° C.
 12. The process of claim 11 whereinsaid temperature is in the range from 175° to 200° C.
 13. The process ofclaim 11 wherein step A) is carried out under a hydrogen pressure in therange of from 50 to 150 bar.
 14. The process of claim 12 wherein step A)is carried out under a hydrogen pressure of from 75 to 125 bar.
 15. Theprocess of claim 1 wherein the process is carried out continuously at anLHSV of 0.05 to 0.7 h⁻¹.
 16. The process of claim 15 wherein said LHSVis from 0.1 to 0.3 h⁻¹.
 17. The process of claim 1 wherein in step A)the molar ratio of polyol to carbonyl compound is from 5:1 to 1:5; thehydrogenation catalyst is present in from 1 to 15% by weight, based onthe weight of said mixture; and step A) is carried out at a temperaturefrom 150° to 250° C. and a hydrogen pressure in the range of from 50 to150 bar.
 18. The process of claim 17 wherein the molar ratio of polyolto carbonyl compound is from 1:1 to 1:4; the hydrogenation catalyst ispresent in from 5 to 15% by weight; said temperature is in the range offrom 175° to 200° C. and said hydrogen pressure is from 75 to 125 bar.19. The process of claim 17 wherein in step A) the at least one polyolis glycerol; in the at least one carbonyl compound R¹ and R²independently of one another represent C₁₋₁₈ alkyl groups; and thehydrogenation catalyst consists of palladium, optionally on an inorganicsupport, present in from 5 to 15% by weight, based on the weight of saidmixture.
 20. The process of claim 19 wherein the at least one carbonylcompound is acetone.